Medical acts performed on the body impose a significant burden on the patient, and thus testing and medical procedures on the body have come to be performed by inserting a medical device such as a catheter directly into a body cavity in place of the conventional approach of making an incision. When using a catheter in this manner, a guide wire is passed through a catheter that is to be introduced to a target site within the body, and then the catheter is guided along the guide wire to that target site.
When inserting a catheter, the guide wire serving as the guide is inserted first and then the catheter is inserted into the body along the guide wire, and when there is little clearance between the catheter and the guide wire, or due to the blood influx at the time of insertion into the body, frictional resistance occurs and causes the guide wire to come into intimate contact with the inner circumferential surface of the catheter, increasing the likelihood of trouble. Consequently, to lower the frictional resistance between the guide wire and the catheter, the guide wire, that is, the core wire, is coated with fluororesin so that the guide wire can pass through the catheter with ease (JP H3-41966A).
However, although a guide wire whose core wire surface has been evenly coated with a fluororesin exhibits lower frictional resistance due to the low friction properties afforded by the fluororesin, the fluororesin comes into intimate contact with the inner circumferential surface of the catheter because it is applied evenly, and thus its effect was not sufficient. Accordingly, other proposals have been forwarded to further reduce the frictional resistance between the catheter and the guide wire, including providing the outer circumferential surface of the guide wire itself with an uneven shape having recessions and protrusions (JP H11-19217A), and wrapping a helical coil around its outside (JP H11-178930A, Tokuhyo 2000-509641).
However, in each of these conventional examples it was necessary to process the core material, and this complicated manufacturing, and there were also problems such as a change in the properties of the wire, for example its strength and modulus of elasticity, due to processing the core material, and an increase in costs due to core material processing, and moreover, there was the problem that the frictional resistance was not significantly improved.